After getting my wifi working, went to admin. and software update.Upon accepting about dozen of updates and additions involving gui and told when done needed to reboot, after the reboot could not get any screen back: would get the "Scientific Linux" heading, then a fade-out and again the SL heading, then sudden black screen with some hard drive blinking for a short time, then nothing but the black screen.Multiple restarts give same result.Of course have command-line and editing options, but not sure what to try.Any suggestions?